Planning Your First DIY Tiling Project

Before you start: a word from the job site

I’ve been laying tile for over twenty years, and the single biggest mistake I see first-timers make isn’t crooked cuts or uneven spacing — it’s running out of materials halfway through the job. Nothing kills momentum like a trip back to the tile shop, only to find out your batch is out of stock and the replacement lot is a slightly different shade.

This guide walks you through the planning side of a tiling project — measuring your space, calculating quantities, and ordering with enough margin that you’re not sweating on install day.

Step 1: Measure your space accurately

Before you even look at tile samples, you need to know exactly how many square feet (or square metres) you’re working with. Here’s how to get it right:

• Rectangular rooms are straightforward: length times width.
• L-shaped rooms need to be split into two rectangles. Measure each one separately and add them together.
• Include recesses and alcoves — they need tile too.
• Don’t subtract small obstacles like toilet flanges or pedestal sinks at this stage. You’ll account for waste later.

Use a steel tape measure, not the fabric kind from a sewing kit. Measure in the same units your tile shop uses — mixing metric and imperial is a recipe for expensive mistakes.

If your space is an unusual shape, the Square Footage Calculator can help you break it into sections:

Write down your total square footage. You’ll need it for every calculation that follows.

Step 2: Work out how many tiles you need

Now that you know your area, you can calculate how many tiles to buy. But there’s a catch — you can’t just divide your floor area by the tile area. You need to factor in:

• Waste from cuts: tiles along walls and around obstacles get cut, and offcuts are often too small to reuse. Budget 10% waste for a simple rectangular room, 15% for rooms with lots of cuts.
• Breakage: even experienced tilers crack the occasional tile. A few spares are insurance.
• Future repairs: keep a small box of matching tiles. If one cracks in five years, you’ll thank yourself.

Let’s use the Tile Calculator to work this out. Enter your room dimensions and tile size, and set your waste percentage:

The calculator gives you both the number of individual tiles and the number of cartons to order. Always round up to full cartons — partial cartons aren’t a thing, and returning unopened boxes is usually straightforward.

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Step 3: Calculate your grout

Grout fills the joints between tiles, and the amount you need depends on three things: tile size, joint width, and tile thickness. Larger tiles with narrow joints use surprisingly little grout. Small mosaic tiles with wide joints use a lot.

A common mistake is buying one bag and assuming it’ll be enough. Here’s the reality: a 25-pound bag of sanded grout covers roughly 80 to 120 square feet of standard floor tile — but that range varies enormously with joint width.

Use the Grout Calculator to get a proper estimate:

Pro tip: buy sanded grout for joints wider than 3mm (⅛ inch) and unsanded for narrower joints. Using sanded grout in thin joints makes them almost impossible to fill evenly.

Step 4: Estimate your thinset mortar

Thinset is the adhesive that bonds tiles to the substrate. The amount depends on your trowel notch size, which depends on your tile size:

• 6mm (¼ inch) square notch: tiles up to 200mm (8 inches)
• 10mm (⅜ inch) square notch: tiles 200–400mm (8–16 inches)
• 12mm (½ inch) square notch: tiles over 400mm (16 inches)

Larger notches lay more mortar per square foot, so big-format tiles use more thinset than you might expect. Let the Thinset Calculator do the maths:

Ordering checklist

Before you place your order, double-check:

• Tiles: order full cartons, rounded up, with your waste factor included
• Grout: buy one extra bag as insurance — unused bags store well in a dry place
• Thinset: check the shelf life (usually 12 months from manufacture) and buy the type matched to your substrate (modified thinset for plywood-backed cement board, unmodified for uncoupling membranes)
• Spacers: buy a bag that matches your intended grout joint width
• Tile levelling clips (optional but recommended for large-format tiles): budget 3–4 per tile

When things don’t go to plan

Even with perfect calculations, real-world tiling has surprises. The substrate might not be perfectly flat. A tile might have a manufacturing defect. Your dog might walk across wet thinset (it’s happened on my jobs more than once).

The buffer in your calculations is there for exactly these moments. If you’ve followed this guide, you’ll have enough material to handle the unexpected — and a few spare tiles in the garage for future repairs.

Good luck with the project. Measure twice, cut once, and take your time with the first row — it sets the line for everything that follows.

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